5.4.1.1 Application Logic

To develop and run the application, follow these steps:

1. Open the main.c file of the project located in the source files folder. Add the following code outside the main() function:

   #define RX_BUFFER_SIZE 1  
   #define TX_BUFFER_SIZE 1
   
   uint8_t rxBuffer;
   uint8_t txBuffer = 0xAA;
   
   volatile bool readStatus_SERCOM_1= false;
   volatile bool writeStatus_SERCOM_1 = false;
   
   volatile bool readStatus_SERCOM_5 = false;
   volatile bool writeStatus_SERCOM_5 = false;
   
   void APP_SERCOM_1_WriteCallback(uintptr_t context)
   {
   SERCOM1_USART_Write(&txBuffer, TX_BUFFER_SIZE);
   }
   
   void APP_SERCOM_1_ReadCallback(uintptr_t context)
   {
   readStatus_SERCOM_1 = true;
   }
   

2. In the following figure, the read callback and write callback is declared. These functions set the pointer to a client function to be called when the given USART’s write or read event occurs. Once the read is completed, the write callback is called and the write function inside this callback writes the data in the console. These callbacks describe the pointer to the function to be called when the write or read event has completed. By setting this to NULL, it will be disabled.

   

3. Inside the main() function, add the following code:

   SYSTICK_TimerStart();
   
    // Extension SERCOM Read and Write Callback
    SERCOM1_USART_WriteCallbackRegister(APP_SERCOM_1_WriteCallback, 0);
    SERCOM1_USART_ReadCallbackRegister(APP_SERCOM_1_ReadCallback, 0);
       
    // Read request for Extension
    SERCOM1_USART_Write(&txBuffer, TX_BUFFER_SIZE);
    SERCOM1_USART_Read(&rxBuffer, RX_BUFFER_SIZE);
   

4. In the following figure, SYS_Initialize (NULL)initializes the modules, such as ports, clock, SERCOM USART, Nested Vector Interrupt Controller (NVIC), and Non-Volatile Memory Controller (NVMCTRL). The callback register functions for read and write operations are declared. Also, the SYSTICK times and the read and write request for SERCOM1 (for extension) is implemented.

   

5. Add the following code inside the while loop:

   SYSTICK_DelayMs(1U);
           
   if(readStatus_SERCOM_1 == true)
   {
   readStatus_SERCOM_1 = false;
   SERCOM1_USART_Read(&rxBuffer, RX_BUFFER_SIZE);
   }
   

6. In the following code example, to visualize the hardware flow control using the RTS and CTS lines, a delay of one millisecond is introduced in the code.